Synthetic and structural studies on C-ethynyl- and C-bromo-carboranes.

A high-yield preparation of the C-monoethynyl para-carborane, 1-Me(3)SiC[triple bond]C-1,12-C2B10H11, from C-monocopper para-carborane and 1-bromo-2-(trimethylsilyl)ethyne, BrC[triple bond]CSiMe(3) is reported. The low-yield preparation of 1,12-(Me3SiC[triple bond]C)2-1,12-C2B10H10 from the C,C'-dicopper para-carborane derivative with 1-bromo-2-(trimethylsilyl)ethyne, BrC[triple bond]CSiMe3, has been re-investigated and other products were identified including the C-monoethynyl-carborane 1-Me3SiC[triple bond]C-1,12-C2B10H11 and two-cage assemblies generated from cage-cage couplings. The contrast in the yields of the monoethynyl and diethynyl products is due to the highly unfavourable coupling process between 1-RC[triple bond]C-12-Cu-1,12-C2B10H10 and the bromoalkyne.

Crystal, molecular and electronic structure of N,N'-diphenyl-N,N'-bis(2,4-dimethylphenyl)-(1,1'-biphenyl)-4,4'-diamine and the corresponding radical cation.

Oxidation of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD, 1 a) and N,N'-diphenyl-N,N'-bis(2,4-dimethylphenyl)-(1,1'-biphenyl)-4,4'-diamine (1 b) with SbCl(5) affords the corresponding radical cations quantitatively. The crystal and molecular structure of 1 b and [1 b]SbCl(6), the first tetraphenyl benzidene derivatives to be characterised crystallographically in both the neutral and radical cation states, reveal molecular parameters in agreement with the predictions made on the basis of DFT studies. Analysis of the NIR transition in the radical cations [1](+) (.